Semi-conductor device



March 1959 A. A. A. M. KOYETS ETAL 2,877,392

SEMI-CONDUCTOR DEVICE Filed Dec. 7, 1954 INVENTORS NTONIUS MARIA KOETS VESSEM US ALOYSIUS A ENRAAD V MUS ANTO AUGUS JAN VERS WILHEL AGENT United States PatentO I SEMI-CONDUCTOR DEVICE Augustinus Aloysius Antonius Maria Koets, Jan Coenraad van Vessem, and Wilhelmus Antonius Roovers, Eindhoven, Netherlands, assignors, by mesne assignments, to North American. Philips Company, Inc., New York, N. Y., a corporation of Delaware Application December 7, 1954, SerialNo. 473,674

Claims priority, application Netherlands December 12, 1953 7 Claims. (Cl. 317-234 This invention relates to semi-conductor devices comprising at least one semi-conductive member. In particular, it relates to a crystal diode or a transistor in a.

. open at both ends.

or seals of the conductors, hereinafter briefly termed" seals, since the said member is unable to withstand high temperatures. The present invention has inter alia for its purpose to avoid undue heating of the semi conductive member during the sealing operation. The invention furthermore permits the heat, evolved in the member by the passage of current, to be more readily dissipated to the outside.-

In accordance with the invention, the space within the envelope exhibits at least two parts whereof the part surrounding a semi-conductive member has a lower specificvresistance (higher heat conductivity) to heat fiow than the part contiguous with a seal.

The first-mentioned part of low specific resistance to heat flow may, for example, consist of fills known per se, which are provided in the fluid state and hardened later, or of viscous fills or pulverulent materials. Several examples will be given later. i

The electrode system may be embedded, if desired prior to introducing it into the envelope, in hardenable material. Subsequently it is introduced into the envelope and, if desired, any spaces remaining filled up.

The last-mentioned part contiguous with the seal may either be vacuum or a gas fill. Alternatively, solid materials such as, for example, glass wool or quartz wool are serviceable as well as powdery materials of poor heat conductivity.

The said diflerence'in resistance to heat flow results in that the heat required for the sealing operation penetrates only with difiiculty to that part of the envelope where the semi-conductive member is located. Moreover, any heat evolved in the said part can easily be carried ofiF, for example by holding the said part in. a cooling clamp.

In order that the invention may readily be carried into elfect it will now be described, by way of example, with reference to the accompanying drawing showing several embodiments thereof and in which Fig. 1 is a sectional view of a transistor during the sealing operation.

Fig. 2 is a sectional view of a crystal diode prior to sealing.

Fig. 3 shows this crystal diode after sealing.

Fig. 4 is a sectional view of a so-called duo-diode.

Figures 5, 8 and 9 are sectional views of transistors and Figures diode.

6 and 7 show two manufacturing phases of a The envelope of the electrode system shown in Fig. 1 comprises a glass tube 1 which is closed at one end with a cover 2 in which three conductors 3 are sealed, which conductors carry an electrode system 4. In this case a so-called alloy transistor is involved, which comprises a semi-conductive member with two fused electrodes (not Separately indicated). The lower end of the tube contains a fill 5, for example silicone grease. This fill may be viscousso as to permit the electrode system to be pressed into it, while the fill invariably maintains its initial position.

After arranging the parts in the position shown in the drawing, the tube 1 is held in a holder or tongs 6 made from metal of good heat conductivity and subsequently the edges of the envelope and of the cover are locally heated to their melting point, as indicated schematically by burners 7, and the cover 2 thus hermetically-sealed to the envelope 1. Preferably, however, the said parts will be heated electrically, either by means of a heater coil or inductively.

The construction shown in Fig. 2, which is particularly suitable for diodes, comprises a glass tube 10 which is The ends are narrowed with regard to the central part of the tube, but at least one opening permits the passage of an electrode system 12. After arranging the system in position, a viscous fill 13 is provided'at the centre of the tube by means of a hollow needle. Subsequently the ends are sealed off, during which treatment the tube is held at its centre in tongs carrying olfthe heat (Fig. 3).

In the same way a duo-diode with centre tap 15 can be made (Fig. 4).

Fig. 5 also shows a transistor. The fill 20 within that part of the envelope which surrounds the semi-c0nduc tive member is a powder of good heat conductivity (low specific resistance to heat flow), for example quartz powder. Alternatively, metal powder such as,

for example, copper or aluminum powder may be used,

but in this case the electrode system and the lower ends of the conductors 3 require to be covered with an insulating layer 21.

For the fill 22 of the upper part of the envelope adjacent the seal, heat-insulating powder (high specific resistance to heat flow) such as, for example, aluminumoxide is chosen. As an alternative, asbestos may be used. This fill 22 mainly serves to hold the fill 20 in place. These fills have the advantage, provided they have been thoroughly cleaned beforehand, that they do not give ofi' any materials adversely affecting the electrode system.

Figs. 6 and 7 show electrode systems. In this instance, the semi-conductive member with the electrodes is first embedded in hardenable material such as, for example, a drop of polystyrene 30 (Fig. 6). The assembly can easily be handled and arranged in an envelope 10, the space surrounding the semi-conductive member 12 being filled up with a preferably viscous fill-31 (Fig. 7). Subsequently the envelope is sealed similarly to Fig. 3.

With regard to the fills the following is to be noted.

As hardenable materials it is advantageous to use ethoxyline resins, commercially available as Araldit and furthermore polyisobutylene.

Suitable viscous fills are polymethylsiloxanes commercially known as silicone grease. A material of this type is commercially sold under the tradename Dow-Corning DC7. The use of viscous materials reduces the risk of cracking of the glass due to stresses. Moreover, the said type of materials have the advantage of very low vapour pressure.

Suitable powdery materials having a low resistance to heat flow are, for example, metal powders, but also a different way of forming suchquartz which may In most cases, the envelope may consist of glass. If

stringent requirements are imposed on the dissipationof heat of the semi-conductivemember, it is alsopossible to make the envelope from metal where it surrounds the semi-conductive member, the remainder consisting of glass.

Two examples-of such electrodesystems are shown in Figures 8 and 9.

In the first example, the envelope consistsof a metal tube 49 which is closed at its bottom end and to which a glass tube 41 is sealed. After introducing the semiconductive member 4 with electrodes and supply conductors 3, the latter are sealed into the glass tube 41,

thus forming a pinch as in incandescent lamps.

In the second example, the envelope again consists of a metal tube 40 which is closed at its bottom end and at the top of which a glass cover ence between the tube and the cover is promoted by the use of enamel having a low melting point.

What is claimed is:

l. A semi-conductor device comprising a relatively small semi-conductive body, a relatively large gas-tight envelope enclosing said semi-conductive body and spaced therefrom, at least one electric conductor extending through said envelope and coupled to said semi-conductive body and heat-sealed into position at one end of said envelope, and a material exhibiting relatively high heat conductivity surrounding the semi-conductive body and filling up the space between the semi-conductor body and the envelope but spaced from the end of said envelope in which the electric conductor is heat-sealed, the space between the end of said envelope in which the electric conductor is heat-sealed and the said high heat conductivity material exhibiting relatively low heat conductivity, whereby heat dissipation of the device during operation is improved, and heat-sealing of the envelope does not detrimentally affect the semi-conductive body.

2. A device as set forth in claim 1 wherein the material is an ethoxylene resin, and the semi-conductive body is embedded in said resin.

3. A device as set forth'in claim 1 wherein the material is a polymethylsiloxane, and the semi-conductive body is embedded in said polymethylsiloxane.

4. A device as set forth in claim 1 wherein the material includes a hardened portion and a viscous portion, said semi-conductive body being embedded in said hardened portion and the latter being embedded in said viscous material.

5. A semi-conductor device comprising a relatively 42 is sealed. The adhersmall semi-conductive body,- a relatively large gas-tight glass envelope enclosing said semi-conductive body and spaced therefrom, at least one electric lead-in conductor heat-sealed in and through one end of said glass envelope and coupled to said'semi-conductive body, and a viscous material exhibiting relativelyhighheat conductivity surrounding the semi-conductive body and filling up the space between envelope but spaced from the end of said envelope-in which the electric conductor is heat-sealed, the space between the end of said envelope in which the electric conductor is heat-sealed and the said high heat conductivity material being vacant, whereby heat dissipation of the device during operation is improved, and heat-sealing of the envelope does not 'detrimentally affect the semiconductive body.

6. A semi-conductor device comprising a relatively small semi-conductive body, a relatively large gas-tight metal envelope enclosing said semi-conductive body-and spaced therefrom and having a glass-end, at least one electric conductor heat-sealed in and'through -said glass end of said envelope and coupled to said semi-conductive body, and a material exhibiting relatively high heat conductivity surrounding the semi-conductive body and filling up the space between the semi-conductive body and the envelope but in which the electric conductor is heat-sealed, the. space between the end of said envelope in which. the electric conductor is heat-sealed and the said high heat conductivity material being vacant, whereby heat, dissipation of the device during operation is improved, and heatsealing of the envelope does not detrimentally afiecttthe semi-conductive body.

7. A semi-conductor device comprising a relatively small. semi-conductive body, a relatively.largergas-tight envelope enclosing said semi-conductive body and spaced therefrom, at least one, electric lead-in conductor. extending through said envelope and'coupled to said semiconductive body and heat-sealed into position at one end of said. envelope, and a mass of metal particles exhibiting relatively high heat conductivity surrounding the semi-conductive body and filling up the space between the semi-conductive body and theenvelope but spaced from the end of said envelope in whichthe electric conductor is heat-sealed, the space between the end of said envelope in which the electric conductor is heat-sealed and the said mass of metal particles exhibiting relatively low heat conductivity, whereby heat dissipation of the device. during operation is improved, and heat-sealing of the, envelope does not detrimentally aflect the semi conductive body.

References Cited in the file of thispatent; UNITED STATES PATENTS 756,676 Midgley Apr. 5, 1904 1,782,129 Andre Nov. 18, 1930. 2,406,405 Salisbury Aug. 27, 1946 2,697,805 Collins Dec. 21, 1954 2,699,594 Bowne Jan. 18, 1955 the semi-conductive body and'the spaced from the end of said'envelope' 

